1. Field of the Invention
The present invention relates to a technique which is used in a slitting line in which a coil of wide metallic band sheet base material is continuously cut into a plurality of band sheets along a longitudinal direction of the band sheet base material for re-coiling. It relates particularly to a multiple endless belt type band sheet coiling tension applying apparatus for applying a proper and uniform coiling tension to all of multiple slit band sheets in a coiling operation after a band sheet base material is slit into band sheets.
2. Description of the Related Art
In any of Japanese Patent Nos. 7074061(B), 3769730(B) and 3947714 (B) and U.S. Pat. No. 3,735,937 which constitute the related art of a multiple endless belt type band sheet coiling tension applying apparatus of our company, a belt pressing portion is constructed so that in an upper belt pressing unit, a hollow space for cooling water is provided directly above the upper belt pressing unit, and in a lower belt pressing unit, an empty space for cooling water is provided directly below the lower belt pressing unit, and these empty spaces are constructed as a completely closed box which enables cooling water to be circulated by a pump provided outside. In addition, in coiling multiple slit band sheets which are made by slitting a wide metallic base material fed from a coil of metallic base material, in order to apply a uniform and proper tension to all the slit band sheets, vertical reinforcement plates are provided in the interior of each of the empty spaces having the box construction so as to minimize the deflection of the belt pressing units which hold the slit band sheets vertically there-between via endless belts, and the reinforcement plates each double as a heat dissipating plate adapted to be in contact with the cooling water in the empty spaces and have a strong construction.
In this multiple endless belt type band sheet coiling tension applying apparatus, the special endless belts, which are each configured as a laminated structure using different types of materials so that friction coefficients of front and back surfaces thereof differ, rotate with their external belt surface sides which have a large friction coefficient closely attached to the corresponding slit band sheets by frictional engagement and at the same time their internal belt surface sides in contact with a pressing surface of the belt pressing unit to generate a tension in the slit band sheets by a relative frictional resisting force there-between. Most of work done to generate the tension is transformed into frictional heat, which increases the temperature of the metallic pressing surface. Unless this frictional heat is removed with good efficiency, the temperature of the pressing surface is increased, whereby the endless belts, which are each the laminated structure made up of a synthetic fiber material and a synthetic resin based material, are damaged by heat and cannot be used any more. Therefore, this frictional heat needs to be removed continuously with good efficiency so as to suppress the increase in temperature of the pressing surface of the belt pressing unit.
In order to enable the continuous operation of the multiple endless belt type band sheet coiling tension applying apparatus by preventing the occurrence of such an overheated state which would damage the endless belts, the empty spaces directly above and below the upper and lower pressing surfaces are configured as cooling water chambers and the plurality of reinforcement plates which double as the heat dissipating plates are disposed in the interior portions of the cooling water chambers, so that cooling water is circulated therein to be in contact with the heat dissipating plates with good efficiency so as to remove continuously the frictional heat generated by sliding friction between the pressing surfaces of the belt pressing units and the internal belt surfaces of the endless belts.
As is seen from the related art, in order to attain the two objects of conducting the frictional heat generated in the pressing surfaces of the belt pressing units to the cooling water chambers with good efficiency and minimizing the deflection of the belt pressing units, it is a common practice that the belt pressing unit is constructed so that the pressing surface which contacts the internal belt surface of the endless belt and the cooling water chamber are integrated into the closed box. Namely, the frictional heat is generated in the internal belt surfaces of the upper and lower endless belts which are held by the upper and lower pressing units and the pressing surfaces of the upper and lower pressing units, and most of the frictional heat so generated moves to back sides of the pressing surfaces by the metallic pressing surfaces which have a higher thermal conductivity than that of the endless belts which are made of the synthetic resin base material and moves further to the cooling water which is in contact with the back sides of the pressing surfaces and the reinforcement plates which each double as the heat dissipating plate.
In conducting the frictional heat to the cooling water with as good efficiency as possible, making thinner a thickness defined between the front surface side of the pressing surface which contacts the endless belt and the back surface side of the pressing surface which contacts the cooling water exhibits better effectiveness. However, a sufficient strength is necessary to generate a uniform frictional force by applying a uniform surface contact pressure over the whole of the pressing surface of each of the upper and lower pressing units by minimizing the deflection thereof, or a thickness needs to be ensured which takes into consideration an abrasion margin for repairing the pressing surface when it wears due to friction, which will be described later. Thus, the pressing surface is designed so as to ensure as thin a thickness as possible which can satisfy these requirements. In the past, our company actually used a multiple endless belt type band sheet coiling tension applying apparatus in which the thickness defined a front surface side and a back surface side of a pressing surface was designed to be increased, and we had an experience that endless belts were overheated to be damaged when the apparatus was operated continuously on a hot day in summer. Thus, we have tried to design the thickness between the front surface side and the back surface side of the pressing surface to be thin since the occurrence of the trouble.
In addition, when this apparatus is used for a long period of time, the pressing surface which contacts the endless belt which runs frictionally receives pressure and hence gradually wears, and irregularities produced on the pressing surface become intense. This causes the multiple slit band sheets to snake or the tension to be applied unevenly, resulting in a failure to coil the slit band sheets produced properly. Thus, as this occurs, the whole structure of the pressing unit including the cooling water chamber which is integrated with the pressing surface has to be replaced. However, the heat dissipating plates which cool the heat from the pressing surface with good efficiency are provided in the cooling water chamber. The pressing unit is made so rigid and strong as not to deflect so as to transmit the pressing force uniformly to the multiple slit band sheets via the endless belts. The pressing surface is finished with a uniform flat plane by elaborate machining, and complex and high-precision work such as wear resistant, hard chrome plating coating is applied to the pressing surface so as to extend the life thereof by reducing wear by the friction of the endless belts. Thus, the replacement of the pressing unit as a whole involves great expense. In addition, the replacement involving disassembling the whole apparatus becomes complex work. Therefore, maintaining the apparatus in operable conditions requires time and labor, constituting the problem that the user has to solve in terms of time and money.
When the wear loss on the pressing surface is small and the irregularities thereon are relatively small, the pressing unit is removed so that the pressing surface is abraded and is finished with hard chrome plating at a shop dedicated to such repair work. Thereafter, the pressing unit is reassembled to the apparatus for use. However, although this repair work involves a relatively large number of days, the slitting line has to be kept operating, and to make this happen, the user is forced to fabricate a whole pressing unit structure as an extra unit structure at great expense for replacement and to repair the worn pressing unit so as to store it as an extra replacement part.
The high degree of flat plane finishing and the hard chrome plating coating are applied to the frictional surface on the front surface of the pressing surface so as to generate a predetermined frictional force by pressing the endless belts uniformly. However, the friction coefficient of the frictional surface which is dry against the internal surfaces of the endless belts becomes unstable, and the tension applied to the slit band sheets via the endless belts is not stabilized. In addition, since the friction coefficient of the dried frictional surface on the front surface of the pressing surface becomes too large, a required difference in friction coefficient between the external belt surface and the internal belt surface of the endless belt cannot be ensured, and the endless belt cannot rotate. Since this causes a fatal trouble of generating scuff marks on the front surfaces of the slit band sheets due to slippage thereof, lubrication of the frictional surface is inevitable. In the related art, a lubricant applying unit is separately disposed so as to cause a lubricant to adhere to the internal belt surfaces of the endless belts, so that the lubricant applying unit is designed to be brought into contact with the internal belt surfaces of the rotating endless belts at an intermediate position along the length thereof, whereby the frictional surface on the front surface of the pressing surface is kept lubricated.
However, since the lubricant component adheres to grooves of pulleys or outer circumferences of oval drums with which the internal belt surfaces of the endless belts are in contact, insufficient lubrication or uneven lubrication occurs on the frictional surface on the front surface of the pressing surface that should be lubricated sufficiently or properly, and in the slitter line where the multiple endless belt type band sheet coiling tension applying apparatus is operated continuously under high load, the front surfaces of the pressing surfaces are overheated, which causes serious the problem that the endless belts are damage, that scuff marks are produced on or dirt adheres to the surfaces of the split band sheets due to the slippage of the endless belts or that the tension cannot be applied uniformly to thereby cause a failure to wind the slit band sheets into a coil. To avoid this problem as much as possible, the slitting line is stopped frequently even during the slitting operation so as to refill lubricant, this leading to a reduction in productivity.
Patent Document 1: Japanese Patent No. 7074061 (B)
Patent Document 2: Japanese Patent No. 3769730 (B)
Patent Document 3: Japanese Patent No. 3947714 (B)
Patent Document 4: U.S. Pat. No. 3,735,937
Since the multiple endless belt type band sheet coiling tension applying apparatus makes use of the friction resisting force between the pressing surfaces of the pressing units and the internal belt surfaces of the endless belts, the wear-resistant hard chrome plating coating is applied to the frictional surfaces on the front surfaces of the pressing surfaces on which the endless belts which are pressed by the upper and lower pressing unit structures so as to extend the lives of the pressing surfaces. However, as has been described above, when the apparatus is used for a long period of time, a wear phenomenon is caused gradually on the frictional surfaces which should be the flat plane to thereby produce irregularities on the frictional surfaces, resulting in unbalanced wear, whereby there is caused a problem that coils of slit band sheets are snaking or the coiling tension is applied unevenly to the multiple slit band sheets. Although the pressing units need to be replaced when the irregularities produced on the frictional surfaces by the wearing thereof grow, as has been described above, the pressing unit is integrated with the cooling water chamber designed to remove the frictional heat to form the complex and strong structure and is precision finished to obtain the uniform surface contact pressure. Thus, depending upon the size of the apparatus, the pressing unit constitutes a replacement part of 1 million yen or more per unit. The replacement work of the integrated pressing unit involves a large scale of work to be actually done for replacement in addition to expense, and the equipment involved in production needs to be put to rest during the replacement of pressing units, disturbing the productivity (the highly expensive replacement part and the large scale of replacement work).
General slitter lines are classified as, for example, a 3-feet (900 mm) type, a 4-feet (1200 mm) type, a 5-feet (1500 mm) type and a 6-feet (1800 mm) type depending upon maximum widths of coils of metallic materials (band sheets) which are handled therein, and in recent years, a slitter line with a maximum width of 2000 mm or larger comes to be used. Although a slitter line is prepared to match an expected maximum coil (band sheet) width, since in many cases most of coils (band sheets) that are slit and fed out from the slitter line are narrower in width than the expected maximum coil width, in the multiple endless belt type band sheet coiling tension applying apparatus, a portion of the pressing surface which lies around a central portion thereof and which is used most wears intensely, whereas portions of the pressing surface which lie on both sides thereof and which are not used frequently wear less. Even in the case of such unbalanced wear, with the pressing unit structure which is configured as the integral unit, the whole of the pressing unit structure needs to be replaced even when minute irregularities are produced by partial wear (even such minute wear requires the replacement of the whole of the pressing unit).
In order to enable the high-speed continuous operation by stabilizing the frictional resistance between the pressing units and the endless belts, the lubrication of the frictional surfaces on the front surfaces of the pressing surfaces becomes important, and to make this happen, the configuration is devised in which the special lubricant is brought into contact with the internal belt surfaces of the endless belts. However, since the lubricant contains lubricating oil and fat which tend to flow out under high temperatures caused by the frictional heat, the lubricating oil contents in the internal surface of the endless belt flow out to the external surface of the endless belt for dispersion from both side edge portions of the endless belt during the rotation of the endless belt by virtue of centrifugal force, as a result of which the lubricating oil contents come to adhere to the surface of the slit band sheet which is in contact with the external belt surface to thereby make dirty the high-grade surface finished slit band sheet, and when this occurs particularly on a surface painted coil or a high-grade plating finished coil (band sheet), the worst case results. In addition, when this lubricating oil contents run out during the operation of the slitter line, the internal belt surface of the endless belt is overheated to be damaged. Therefore, even in the midst of coiling the slit band sheets, the coiling operation needs to be stopped so that lubricant is refilled or the edge portions of the endless belt are cleaned so as to remove extra lubricating oil contents which flow out there-from. As a countermeasure there-against, the realization of a multiple endless belt type band sheet coiling tension applying apparatus is eagerly desired which can maintain a constant lubricated state without using liquid lubricating oil and fat (external lubrication which is characteristic of troublesome maintenance and inspection).